Session
Cloning

Session cloning refers to the ability of forwarding an input to
multiple output QAM channels. Only multicast sessions can be cloned. The output
QAM channels are located on the same or different line cards. However, an input
cannot be cloned on the same QAM channel. Cloning is available on session-based
GQIv2 or Table-based sessions. It is applicable to re-mapped, pass-through, and
data piping sessions. All cloned sessions must have the same processing type,
bitrate and jitter value. For re-mapped sessions, each output copy will have a
different output program number.

Redundant
Multicast Sources

The redundant
multicast sources feature supports up to four SSM/ASM multicast address pairs
per video session. However, only multicast traffic from one source is forwarded
to the output QAMs. When the active source fails, another source is chosen
automatically. Multicast sources must be unique within a redundant group and
cannot overlap across redundant groups.

The order of the sources is critical when multicast sessions are configured via GQI or VSRM. For a given group IP address, the source IP addresses must be specified in the same order.

For example: The group IP address 232.1.2.3 used with two sessions must have the source IP addresses specified in the same order.

Session A configured with group IP 232.1.2.3 source 174.2.3.4 source2 174.4.5.6 source3 174.7.8.9 and session B or any session created after session A configured using group IP 232.1.2.3, must have the source IP addresses in this same order as specified for session A. That is, source 174.2.3.4 source2 174.4.5.6 source3 174.7.8.9.

This ensures that all sessions switch to the same source IP address when a source switch occurs. Additionally, sessions configured via GQI have up to three sources available for redundancy, whereas multicast labels configured for table-based sessions have up to four sources available for redundancy.

Multicast labels
must use unique groups and S/G pairs. These pairs cannot be used by other
multicast labels or by multicast sessions that use S/G pairs. For example, when
one multicast session uses {[S1, G], [S2, G] and [S3, G]}, another session
cannot use {[S1, G], [S4, G]}.

Multicast source
change is based on the session state; INIT, IDLE, ACTIVE or OFF. A session
configured for the first time is in INIT state and stays in this state for a
brief time. If traffic starts before the INIT timer expires, it moves to the
ACTIVE state, otherwise to the IDLE state.

When traffic starts,
the session remains in ACTIVE state as long as traffic continues to flow. When
traffic stops for a time longer than the IDLE timer, the session moves to IDLE
state. During IDLE state, PAT and PMT of the session is retained as the output.
If traffic resumes in this state, the session moves to ACTIVE state again with
all its previous PSI and remapping information unaltered.

In IDLE state, if
traffic does not start or resume before the OFF timer expires, the session
transitions to OFF state. When traffic resumes for a session in OFF state, it
is treated as a new session.

Sessions that
transition from ACTIVE to IDLE have higher priority and will be moved to the
backup source than those that were newly created and have changed from INIT to
IDLE.

Benefits of
Switched Digital Video

Switched Digital Video provides
the following benefits:

Saves space, maintenance and
cost.

Allows customers to oversubscribe bandwidth.

Prerequisites for
Switched Digital Video

To access multicast
capability, configure multicast routing.

To switch sources for table-based sessions, configure at least two
sources for a multicast label and then associate with the desired session.

Restrictions for
Switched Digital Video

While creating a multicast
label, up to four sources can be associated with one group IP address.

Labels are used with table-based video sessions only.

Sessions created with GQI Tools do not use labels. However, they
can have up to three sources associated with one group IP address.

QAM
Sharing

Unicast and
multicast video sessions can co-exist on the same QAM channel for VOD, SDV or
Gaming sessions. QAM sharing requires a common Edge Resource Manager to avoid
oversubscription of QAM resources between services.

Note

QAM sharing
with MPTS pass-thru sessions is not supported.

QAM
Replication

Multicast
sessions can be replicated from one port to other ports on the same line card
and/or across line cards.

The difference
between a cloned session and replicated sessions is:

Cloned
sessions are initiated by a user on session creation. Each session has a unique
session id and may have different output configuration.

Replicated
sessions have the same output configuration attributes. For sessions that are
replicated across line cards, session on each line card will have its own
unique session id.

MPTS Pass-through
Session

The MPTS session is assumed to have no collision in the PID space and
program number space with other sessions that already exist within a QAM.
Hence, SPTS remap and MPTS pass-through sessions cannot co-exist on the same
QAM. Otherwise, there might be conflict when the PID and program numbers in the
MPTS and SPTS remuxing are not unique on the output QAM channel.

For a pass-through session:

The PAT is snooped and regenerated with the correct TSID.

The PMT and other program data are not changed.

PID remapping is not performed.

Input NULL packets are dropped.

Oversubscription results in random TP dropping, and all ghost PIDs
are preserved in the output.

Configuring
Multicast Routing

You can enable IP
Multicast Distributed Switching (MDS) to provide distributed switching of
multicast packets received at the line cards.

Configuring
Multicast Label

The Cisco cBR-8
router supports up to four multicast address pairs per multicast session for
backup purpose. To specify additional sources for a multicast session for
table-based, a label needs to be configured and attached to the session
configuration. A maximum of 2000 multicast labels can be created but only 2048
multicast addresses can be active at a time.

Multicast label is
used for table-based session configuration when more than one multicast source
[S, G] is used as backup for the sessions. A mullticast label can only be
created or deleted; it cannot be modified. The multicast label cannot be
deleted before the sessions using it are removed.

Groups used by multicast labels must be unique like the multicast S/G
pairs. However, sources may be used by more than one label as long as the group
is unique. A maximum of 4 multicast sources is allowed in one label. If the
label is used in multiple sessions, the sessions are considered as cloned
sessions.

Configuring
Multicast Table-based Sessions

Similar to
table-based unicast session configuration, sessions can be configured as
individual sessions under each QAM carrier that is assigned to a table-based
LED.

A multicast
session can be configured with a single input multicast input source or
multiple input sources for backup purpose. For multiple backup sources, a label
is required to be associated with the session configuration. Same label can be
applied to multiple sessions on different QAM channel. These sessions are
considered as cloned sessions.

For session
cloning on multiple QAMs within the same line card, only one copy of the
traffic is forwarded to the line card. The line card replicates the input
packets and forwards them to multiple QAMs. Each cloned copy of a remapped
session will have the same or different output program number.

Configuring Source
Switching

Source switching happens
automatically when the current source goes down. If more than one source IP is
configured, the software will automatically switch to the next valid source IP,
if it is available. However, to force switch from one valid source to another
valid source, use the following commands:

Feature Information for Switched Digital Video

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http:/​/​www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Note

The table below lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Feature Name

Releases

Feature Information

Switched Digital Video

Cisco IOS XE Everest 16.5.1

This feature was integrated on the Cisco cBR Series Converged Broadband Routers.